Intermediates in the preparation of indolobenzoxazepines

ABSTRACT

This invention relates to substituted indolobenzoxazepines which act as central nervous system depressants and as such are useful as tranquillizers.

This is a division, of application Ser. No. 620,734 filed Oct. 8, 1975, now U.S. Pat. No. 4,013,641.

This invention relates to substituted indolobenzoxazepines of the following general formula: ##STR1##

In this formula, R₁ may be hydrogen, lower alkyl of 1 to 6 carbon atoms or an aralkyl group of 1 to 6 carbon atoms in the chain; R₂ may be hydrogen, a halogen atom such as fluorine or chlorine, lower alkyl of 1 to 6 carbon atoms or a trifluoromethyl group. "A" may be a methylene group or a carbonyl group. R₃ may be hydrogen, lower alkyl of 1 to 6 carbon atoms, an aralkyl group of 1 to 6 carbon atoms in the chain, or an ω-aminoalkyl group of the formula ##STR2## in which n may be 2 to 4 and R₄ may be hydrogen, lower alkyl of 1 to 6 carbon atoms or, taken together with the N atom may form a heterocyclic ring of the formula ##STR3## wherein X may be oxygen, sulfur, --CH₂ CH₂ --; a bond connecting the adjacent carbon atoms or CH-R₅ or N-R₅ wherein R₅ may be hydrogen or lower alkyl of 1 to 6 carbon atoms.

The products of this invention may be prepared according to the following reaction sequence starting with an ester of indoxylic acid, II: ##STR4##

In structure II, R is a lower alkyl group of 1 to 6 carbon atoms and R₁ is as defined for I. These starting materials are known and were prepared according to methods described in the literature.

In the first step, the indoxylate ester is alkylated with an appropriately substituted o-halonitrobenzene of structure III to give an intermediate according to structure IV. In structure III, hal. refers to halogen and may be fluorine, chlorine, bromine or iodine. R₂ is as defined for structure I. This alkylation is carried out in a solvent such as a lower alcohol, THF, or, preferably, DMF in the presence of a weak base such as potassium carbonate.

In the second step, the nitro group of intermediate IV is reduced to give an amino group, as shown in structure V: ##STR5##

This reduction can be done catalytically in a solvent such as ethanol and using a catalyst such as platinum oxide, palladium on carbon or Raney Nickel, or it may be done chemically in a solvent such as ethanol using a metal such as iron filings or zinc dust in the presence of an acid such as hydrochloric or acetic.

In the third step, the amino ester of structure V is hydrolyzed to give the amino acid of structure VI: ##STR6##

This hydrolysis is best carried out in an aqueous-alcoholic solvent system using an alkali metal hydroxide such as sodium or potassium hydroxide.

Alternatively, the order of sequence of the reduction and hydrolysis steps may be reversed so that intermediate IV is first hydrolyzed to afford a nitro acid of structure VII which is subsequently reduced to give VI. ##STR7##

In the fourth step, ring closure of aminoacid VI to lactam VIII is carried out in a solvent such as ethanol or, preferably, THF, using an amide forming reagent such as dicyclohexylcarbodiimide, or, preferably, ethyl 1,2-dihydro-2-ethoxy-1-quinoline carboxylate. ##STR8##

In the fifth step, lactam VIII is alkylated with an appropriately substituted halide, R₃ hal., to give a product of structure IX. The halides for this alkylation are selected from the group consisting of halides of lower alkanes of 1 to 6 carbon atoms, aralkyl halides containing 1 to 6 carbon atoms in the chain, or ω-aminoalkyl halides of the formula: ##STR9## in which hal., n and R₄ are as previously defined.

The alkylation is best carried out in polar aprotic solvents such as DMF or DMSO using a strong base such as sodium or potassium hydride or amide as the catalyst. ##STR10##

In the final step, the compound of structure IX is reduced to afford a compound according to structure X. This reduction is best carried out with a complex hydride reagent such as lithium aluminum hydride in a solvent such as ether or THF. ##STR11##

In order to prepare products in which R₁ is other than hydrogen, two methods may be used. In the first method, an R₁ substituted indoxylic ester is employed in step 1. Such starting materials may be synthesized according to the procedure exemplified in example 14. In the second method, an alkylation step may be carried out on structure IV wherein R₁ = H. This alkylation is best carried out using a polar aprotic solvent such as THF, DMF or DMSO and a strong base such as sodium hydride or potassium amide as solvent. Among the alkylating agents which may be used are halides of alkanes of 1 to 6 carbon atoms, or aralkyl halides of 1 to 6 carbon atoms in the chain.

In order for a more thorough understanding of the subject matter of this application, the following examples are given:

EXAMPLE 1 ##STR12## Methyl-3-[o-nitrophenoxy]-indole-2-carboxylate

A mixture of 5.73g (0.03 mole) of methyl indoxylate, 4.23g (0.03 mole) of o-fluoronitrobenzene, 4.14g (0.03 mole) of potassium carbonate and 50ml of DMF was heated with stirring for 6 hours on the steam bath. The mixture was cooled, poured into water and filtered to give 6.7g of crude product. Recrystallization from acetonitrile gave analytical material, mp. 201°-2°.

Anal. Calcd. for C₁₆ H₁₂ N₂ O₅ : C, 61.54; H, 3.87; N, 8.97. Found: C, 61.39; H, 3.92; N, 8.45.

EXAMPLE 2 ##STR13## Methyl-3-[o-aminophenoxy]-indole-2-carboxylate

A mixture of 3.12g of methyl-3-[o-nitrophenoxy]-indole-2-carboxylate, 10g of 40 mesh iron filings, 5ml of 5% aqueous acetic acid and 300ml of ethanol was refluxed with stirring for 3 hours. The mixture was filtered and concentrated to a solid. Recrystallization from ethanol gave analytical material, mp. 183°-4°.

Anal. Calcd. for C₁₆ H₁₄ N₂ O₃ : C, 68.08; H, 5.00; N, 9.92. Found: C, 67.88; H, 5.19; N, 9.93.

EXAMPLE 3 ##STR14## 3-[o-aminophenoxy]-indole-2-carboxylic acid

1.6g of methyl-3-[o-aminophenoxy]-indole-2-carboxylate was dissolved in 10ml each of ethanol and water and refluxed for 10 min. The clear solution was acidified with acetic acid. The white precipitate was filtered and recrystallized from acetonitrile to give analytical material, mp. 217°-18°.

Anal. Calcd. for C₁₅ H₁₂ N₂ O₃ : C, 67.15; H, 4.51; N, 10.44. Found: C, 66.94; H, 4.59; N, 10.47.

EXAMPLE 4 ##STR15## 7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one

A solution of 1.5g of 3-[o-aminophenoxy]-indole-2-carboxylic acid in 50ml of THF was treated with 1.48g of EEDQ and the clear solution left 18 hours at ambient temperature. The THF was removed by distillation, and the residue was rubbed with 2N HCl to give a yellow solid. Recrystallization from ethanol gave analytical material, mp. 233°-4°.

Anal. Calcd. for C₁₅ H₁₀ N₂ O₂ : C, 71.97; H, 4.03; N, 11.20. Found: C, 71.96; H, 4.02; N, 11.21.

EXAMPLE 5 ##STR16## Methyl-3-[o-nitrophenoxy]-1-methyl-indole-2-carboxylate

6.73g (0.16 mole) of 57% sodium hydride in mineral oil was washed with hexane and suspended in 500ml of THF. To this was added 43.4g (0.139 mole) of methyl-3-[o-nitrophenoxy]-indole-2-carboxylate. The mixture ws stirred at reflux for 1 hour, then 42.6g (0.3 mole) of methyl iodide was added and reflux continued for 3 hours. Water (5ml) was added, the THF removed by distillation and the gummy residue recrystallized from isopropanol to give analytical material as yellow needles, mp. 119°-21°.

Anal. Calcd. for C₁₇ H₁₄ N₂ O₅ : C, 62.57; H, 4.32; N, 8.59. Found: C, 62.68; H, 4.38; N, 8.72.

EXAMPLE 6 ##STR17## Methyl-3[o-aminophenoxy]-1-methyl-indole-2-carboxylate

In the same way as described in example 2, methyl-3-[o-nitrophenoxy]-1-methylindole-2-carboxylate was reduced and the crude product recrystallized from methanol to give analytical material, mp. 103°-5°.

Anal. Calcd. for C₁₇ H₁₆ N₂ O₃ : C, 68.90; H, 5.44; N, 9.45. Found: C, 68.75; H, 5.60; N, 9.58.

EXAMPLE 7 ##STR18## 3-[o-aminophenoxy]-1-methyl-indole-2-carboxylic acid

In the same way as described in example 3, methyl-3-[o-aminophenoxy]-1-methyl-indole-2-carboxylate was hydrolyzed and the crude product recrystallized from ethanol to give analytical material, mp. 193°-4°.

Anal. Calcd. for C₁₆ H₁₄ N₂ O₃ : C, 68.07; H, 5.00; N, 9.92. Found: C, 67.94; H, 5.22; N, 9.97.

EXAMPLE 8 ##STR19## 7-methyl-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one

In the same way as described in example 4, 3-[o-aminophenoxy]-1-methyl-indole-2-carboxylic acid was cyclized with EEDQ. Analytical material was obtained by recrystallization from acetonitrile, mp. 247°-8°.

Anal. Calcd. for C₁₆ H₁₂ N₂ O₂ : C, 72.71; H, 4.58; N, 10.60. Found: C, 72.69; H, 4.66; N, 10.85.

EXAMPLE 9 ##STR20## Methyl-3-[2-nitro-4-chlorophenoxy]-indole-2-carboxylate

In the same way as described in example 1, methylindoxylate and 2,5-dichloronitrobenzene were reacted. Recrystallization from ethanol gave analytical material, mp. 171°-2°.

Anal. Calcd. for C₁₆ H₁₁ N₂ O₅ Cl: C, 55.43; H, 3.20; N, 8.08; Cl, 10.72. Found: C, 55.24; H, 3.48; N, 7.88; Cl, 10.50.

EXAMPLE 10 ##STR21## Methyl-3-[2-nitro-4-chlorophenoxy]-1-benzyl-indole-2-carboxylate

In the same way as described in example 5, methyl-3-[2-nitro-4-chlorophenoxy]-indole-2-carboxylate was alkylated with benzyl bromide. Analytical material was obtained by recrystallization from ethanol, mp. 120°-1°.

Anal. Calcd. for C₂₃ H₁₇ N₂ O₅ Cl: C, 63.24; H, 3.92; N, 6.41; Cl, 8.12. Found: C, 63.15; H, 3.97; N, 6.39; Cl, 8.30.

EXAMPLE 11 ##STR22## Methyl-3-[2-amino-4-chlorophenoxy]-1-benzyl-indole-2-carboxylate

In the same way as described in example 2, methyl-3-[2-nitro-4-chlorophenoxy]-1-benzyl-indole-2-carboxylate was reduced and the crude product recrystallized from ethanol to give analytical material, mp. 121°-3°.

Anal. Calcd. for C₂₃ H₁₉ N₂ O₃ Cl: C, 67.90; H, 4.71; N, 6.88; Cl, 8.71. Found: C, 67.85; H, 4.80; N, 6.76; Cl, 8.96.

EXAMPLE 12 ##STR23## 3-[2-amino-4-chlorophenoxy]-1-benzyl-indole-2-carboxylic acid

In the same way as described in example 3, methyl-3-[2-amino-4-chlorophenoxy]-1-benzyl-indole-2-carboxylate was hydrolyzed and the crude product recrystallized from 95% ethanol to give analytical material, mp. 218°-19°.

Anal. Calcd. for C₂₂ H₁₇ N₂ O₃ Cl: C, 67.26; H, 4.36; N, 7.13; Cl, 9.02. Found: C, 67.17; H, 4.40; N, 7.05; Cl, 9.19.

EXAMPLE 13 ##STR24## 3-chloro-7-benzyl-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one

In the same way as described in example 4, 3-[2-amino-4-chlorophenoxy]-1-benzyl-indole-2-carboxylic acid was cyclized, and the crude product was recrystallized from aqueous THF to give analytical material, mp. 259°-61°.

Anal. Calcd. for C₂₂ H₁₅ N₂ O₂ Cl: C, 70.50; H, 4.03; N, 7.47; Cl, 9.46. Found: C, 70.48; H, 4.12; N, 7.20; Cl, 9.59.

EXAMPLE 14 ##STR25## Ethyl-N-methyl indoxylate

A mixture of 38.8g (0.2 mole) of ethyl chloromalonate and 44g (0.41 mole) of N-methylaniline was heated on the steam bath for 72 hours. After cooling, the mixture was diluted with 500ml of methylene chloride and unreacted N-methylaniline extracted with 4N HCl. The methylene chloride layer was dried and concentrated to 49g of oil. This was diluted with 49ml of hexamethylphosphoramide, and the mixture was heated rapidly to boiling (bath temp. 245°). Reflux was continued for 20 minutes, the mixture cooled rapidly and poured into 400ml of 4N HCl. The crude solid product was filtered and recrystallized from isopropanol to give crystals, mp. 95°-6°.

EXAMPLE 15 ##STR26## Ethyl-3-[2-nitro-4-chlorophenoxy]-1-methyl-indole-2-carboxylate

In the same way as described in example 1, ethyl-N-methyl indoxylate was alkylated with 2,5-dichloro nitrobenzene and the crude product recrystallized from isopropanol to give analytical material, mp. 133°-4°.

Anal. Calcd. for C₁₈ H₁₅ N₂ O₅ Cl: C, 57.69; H, 4.03; N, 7.47; Cl, 9.46. Found: C, 57.97; H, 4.09; N, 7.47; Cl, 9.70.

EXAMPLE 16 ##STR27## Ethyl-3-[2-amino-4-chlorophenoxy]-1-methyl-indole-2-carboxylate

In the same way as described in example 2, ethyl-3-[2-nitro-4-chlorophenoxy]-1-methyl-indole-2-carboxylate was reduced and the crude product recrystallized from ethanol, mp. 118°-20°.

Anal. Calcd. for C₁₈ H₁₇ N₂ O₃ Cl: C, 62.70; H, 4.97; N, 8.12; Cl, 10.28. Found: C, 62.82; H, 5.07; N, 8.05; Cl, 10.56.

EXAMPLE 17 ##STR28## 3-[2-amino-4-chlorophenoxy]-1-methyl-indole-2-carboxylic acid

In the same way as described in example 3, ethyl-3-[2-amino-4-chlorophenoxy]-1-methyl-indole-2-carboxylate was hydrolyzed and the crude product recrystallized from 95% ethanol to give analytical material, mp. 204°-6°.

Anal. Calcd. for C₁₆ H₁₃ N₂ O₃ Cl: C, 60.67; H, 4.14; N, 8.84; Cl, 11.19. Found: C, 60.70; H, 4.21; N, 8.90; Cl, 11.09.

EXAMPLE 18 ##STR29## 3-chloro-7-methyl-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one

In the same way as described in example 4, 3-[2-amino-4-chlorophenoxy]-1-methyl-indole-2-carboxylic acid was cyclized, and the crude product, insoluble in all solvents, was purified by digesting for 1 hour in hot THF and filtering while hot, mp. 306°-7°.

Anal. Calcd. for C₁₆ H₁₁ N₂ O₂ Cl: C, 64.33; H, 3.71; N, 9.38; Cl, 11.87. Found: C, 64.20; H, 3.73; N, 9.15; Cl, 12.40.

EXAMPLE 19 ##STR30## 7-methyl-5-(3-piperidinopropyl)-7H-indolo[3,2-b][1,5]benzoxazepin-6(5H)-one hydrochloride

A mixture of 1.8g of 7-methyl-7H-indolo [3,2-b][1,5]benzoxazepin-6(5H)-one, 0.42g of 57% sodium hydride-mineral oil dispersion and 10ml of THF was refluxed for 15 min. and then treated with 4.0g of 3-chloropropylpiperidine. The mixture was refluxed for 24 hrs., diluted with 2N HCl and extracted with ether. The aqueous layer was made basic with 5% NaOH and the oil extracted with ether. The ether phase was dried and treated with dry HCl to give a white solid. The solid was recrystallized from methanol-ether to give analytical material, mp. 205°-6°.

Anal. Calcd. for C₂₄ H₂₇ N₃ O₂.HCl: C, 67.67; H, 6.63; N, 9.86; Cl, 8.32. Found: C, 67.56; H, 6.78; N, 9.72; Cl, 8.59.

EXAMPLE 20 ##STR31## 7-methyl-5-(3-morpholinoethyl)-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one hydrochloride

In the same way as described in example 19, 7-methyl-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one was alkylated with 2-(chloroethyl)morpholine and the crude hydrochloride recrystallized from ethanol to give analytical material, mp. 266°-8°.

Anal. Calcd. for C₂₂ H₂₃ N₃ O₃.HCl: C, 63.84; H, 5.84; N, 10.15; Cl, 8.57. Found: C, 63.58; H, 5.86; N, 10.25; Cl, 8.49.

EXAMPLE 21 ##STR32## 7-methyl-5-[(2-dimethylamino)ethyl]-7H-indolo-[3,2-b][1,5]benzoxazepine-6(5H)-one

In the same way as described in example 19, 7-methyl-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one was alkylated with dimethylaminoethyl chloride, and the crude base obtained by removal of the ether was recrystallized from methanol, mp. 119°-21°.

Anal. Calcd. for C₂₀ H₂₁ N₃ O₂ : C, 71.62; H, 6.31; N, 12.53. Found: C, 71.66; H, 6.40; N, 12.69.

EXAMPLE 22 ##STR33## 7-benzyl-3-chloro-5[2-(dimethylamino)ethyl]-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one maleate

In the same way as described in example 19, 3-chloro-7-benzyl-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one was alkylated with dimethylaminoethyl chloride. The crude-free base gave a crystalline salt on treatment with maleic acid in ethanol. Recrystallization from isopropanol gave analytical material, mp. 168°-70°.

Anal. Calcd. for C₂₆ H₂₄ N₃ O₂ Cl.C₄ H₄ O₄ : C, 64.11; H, 5.02; N, 7.48; Cl, 6.31. Found: C, 63.98; H, 5.06; N, 7.34; Cl, 6.60.

EXAMPLE 23 ##STR34## 7-benzyl-3-chloro-5-[(2-dimethylamino)ethyl]-6,7-dihydro-5H-indolo[3,2-b][1,5]benzoxazepine maleate

A solution of 7.8g of 7-benzyl-3-chloro-5[(2-dimethylamino)ethyl]-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one in 100ml of ether was added dropwise to a suspension of 0.76g of lithium aluminum hydride in ether. The mixture was stirred for 18 hours at ambient temperature, decomposed with saturated NH₄ Cl solution, and the alumina filtered and washed with ether. The ether solution was concentrated to a gum; the gum taken up in ethanol and treated with 2.0g of maleic acid. The crude salt was recrystallized from ethanol for analysis, mp. 149°-51°.

Anal. Calcd. for C₂₆ H₂₆ N₃ OCl.C₄ H₄ O₄ : C, 65.75; H, 5.52; N, 7.67; Cl, 6.47. Found: C, 64.10; H, 5.73; N, 7.20; Cl, 6.44.

EXAMPLE 24 ##STR35## 7-benzyl-3-chloro-5-[(3-dimethylamino)propyl]-7H-indolo-[3,2-b][1,5]benzoxazepine-6(5H)-one hemifumarate

In the same way as described in example 19, 3-chloro-7-benzyl-7H-indolo[3,2-b][1,5]benzoxazepine-6(5H)-one was alkylated with 3-dimethylaminopropyl chloride. The crude base was treated with fumaric acid in ethanol and the salt recrystallized from methanol, mp. 203°-5°.

Anal. Calcd. for C₂₇ H₂₆ N₃ O₂ Cl.1/2C₄ H₄ O₄ : C, 67.24; H, 5.45; N, 8.11; Cl, 6.84. Found: C, 67.25; H, 5.51; N, 7.93; Cl, 6.41.

EXAMPLE 25 ##STR36## 7-benzyl-3-chloro-5-[3-(dimethylamino)propyl]-6,7-dihydro-5H-indolo[3,2-b][1,5]benzoxazepine furmarate

In the same way as described in example 23, 7-benzyl-3-chloro-5-[(3-dimethylamino)propyl]-7H-indolo-[3,2-b][1,5]benzoxazepine-6(5H)-one was reduced. The crude base in ethanol was treated with furmaric acid and the salt recrystallized from ethanol, mp. 146°-7°.

Anal. Calcd. for C₂₇ H₂₈ N₃ OCl.C₄ H₄ O₄ : C, 66.25; H, 5.74; N, 7.48; Cl, 6.31. Found: C, 66.45; H, 5.84; N, 7.33; Cl, 6.39.

EXAMPLE 26 ##STR37## 3-chloro-7-methyl-5-(2-piperidinoethyl)-7H-indolo-[3,2-b][1,5]benzoxazepine-6(5H)-one

In the same way as described in example 19, 3-chloro-7-methyl-7H-indolo[3,2-b][1,5]benzoxazepin-6(5H)-one was alkylated with piperidinoethyl chloride. The crude solid base was recrystallized from acetonitrile, mp. 160°-2°.

Anal. Calcd. for C₂₃ H₂₄ N₃ O₂ Cl: C, 67.39; H, 5.90; N, 10.25; Cl, 8.65. Found: C, 67.34; H, 5.94; N, 10.10; Cl, 8.56.

EXAMPLE 27 ##STR38## 3-chloro-7-methyl-5-(3-piperidinopropyl)-7H-indolo-[3,2-b][1,5]benzoxazepin-5(5H)-one hydrochloride

In the same way as described in example 19, 3-chloro-7-methyl-7H-indolo-[3,2-b][1,5]benzoxazepin-6(5H)-one was alkylated with 3-chloropropyl piperidine, and the crude salt was recrystallized from isopropanol, mp. 202°-4°.

Anal. Calcd. for C₂₄ H₂₆ N₃ O₂ Cl.HCl: C, 62.61; H, 5.91; N, 9.13; Cl, 15.40. Found: C, 62.31; H, 5.98; N, 9.12; Cl, 15.37.

The compounds of this invention are CNS depressants and as such are useful as tranquillizers. Thus the compound of structure XI is active in blocking conditioned avoidance in rats at doses as low as 10 mg/kg. The compound of structure XII was a depressant of motor activity in rats at 31 mg/kg. 

I claim:
 1. Compounds of the general formula
 2. The compound according to claim 1 which is
 3. The compound according to claim 1 which is 3-[2-amino-4-chlorophenoxy]-1-methyl-indol-2-carboxylic acid. 